Sensing edges have been used for a long time in commercial applications. In such commercial applications, a sensing edge is secured to the leading edge of a door, typically an overhead-type door which is opened and closed utilizing a motor-powered actuator. Such prior sensing edges generally include some form of switch means or switch extending substantially along the entire length of the leading edge of the door such that if an object is in the path of a closing door, pressure from the object is applied to the sensing edge to either make or break electrical contact within the switch. The sensing edge is connected to the door actuator in such a manner that the making or breaking of contact by the switch within the sensing edge results in the actuator either immediately stopping further closing movement of the door or immediately reversing movement of the door.
While sensing edges of this type have been in use in the industrial and commercial sector for a substantial period of time, until recently, sensing edges of this type have not been used in the residential area. The U.S. government has now acted to require that residential garage door openers include some type of quick acting sensor for the purpose of stopping the lowering or closing of a residential garage door or reversing the downward or closing movement of a residential garage door when an object or person is located within the path of the garage door. As a result, manufacturers of residential garage door openers have designed, redesigned or modified their products in order to permit a sensing edge or other sensing device to be employed for this purpose. Most of the new or modified automatic garage door openers which are now on the market employ a "fail sale" system in which the garage door opener or actuator is required to continuously receive some type of predetermined signal from the sensing edge or other sensing device employed. Thus, whenever there is any interruption in the predetermined signal, the garage door opener/actuator immediately stops the closing of a garage door or reverses the closing garage door.
Unfortunately, no governmental or universal standards were developed for the predetermined signal which the various garage door opener/actuators must receive in order to permit continued normal (fail-safe) operation. Thus, each of the residential garage door opener manufacturers have developed its own signal which its own garage door opener/actuator must receive for continued normal operation. The signals vary greatly from manufacturer to manufacturer. The opener/actuators of some manufacturers must receive a generally continuous voltage between predetermined minimum and/or predetermined maximum voltage levels which vary from manufacturer to manufacturer. The opener/actuators of other manufacturers are more sophisticated in that they must receive a generally continuous pulse train of individual pulses having differing maximum and minimum voltages and having differing periods, pulse widths, etc. Thus, it was necessary to develop a separate sensing edge adapted to provide the necessary signal for each different manufacturer's garage door opener/actuator.
The present invention relates to a single sensing device which includes a sensing edge and an electrical circuit, called a termination circuit, which serves as a universal interface so that the sensing device can be utilized with the garage door opener/actuator of various manufacturers. The use of the present invention is advantageous in that it precludes the necessity for designing, developing and producing a plurality of individual sensing edges, each adapted for use with a separate manufacturer's garage door opener/actuator.